Vietnam's biggest oil refinery, the $9-billion Nghi Son, started commercial operations in late 2018, and has a capacity of 200,000 barrels per day (bpd).

"The refinery will be fully operational in days, around a week," and the shutdown had not caused any damage, said a source with direct knowledge of the matter, who sought anonymity in the absence of authorisation to speak to the media.

The refinery, located 260 km (160 miles) south of Hanoi, is 35.1% owned by Japan's Idemitsu Kosan Co, 35.1% by Kuwait Petroleum, 25.1% by PetroVietnam and 4.7% by Mitsui Chemicals Inc.

Nghi Son and the 130,000-bpd Dung Quat refinery, which started production in 2009, together meet about 70% of Vietnam's demand for refined oil products.

(Reporting by Khanh Vu; Editing by Clarence Fernandez and Devika Syamnath)

By Khanh Vu